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The US Open champion started slowly but came to terms with humid conditions and pulled out some impressive ground strokes on the way to a 6-4 6-2 victory in 87 minutes.
American qualifier Chirico came undone with 42 unforced errors to Raducanu's 18, while the world No19 won 76 per cent of her first and second serves.
Second seed Raducanu broke Chirico's serve to take a 3-2 lead in the second set and closed out the match from there.
Raducanu, who will face Camila Osorio in the second round, was satisfied with her win.
“It definitely feels really good to get a win here in DC,” she said in her post-match press conference.
“After not playing for quite a bit after Wimbledon or many matches at all this year, I think it's a really nice feeling just to get on the board.
“I think playing any first round is always pretty challenging. Then when you're not necessarily that match-sharp, small things you don't necessarily get right. It's just important to stay calm.”
Next opponent Osorio was bundled out by Harriet Dart in the first round at the Rothesay Classic Birmingham in June, after the 67th-ranked Colombian defeated returning-from-injury former Australian Open champion Sofia Kenin in straight sets.
Raducanu's singles win came one day after after her professional doubles debut alongside fellow teenager Clara Tauson ended with a straight-sets loss in the US capital.
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Earlier, Dan Evans secured his place in the third round with a straight-sets victory over fellow Briton Kyle Edmund.
The 32-year-old 16th seed made short work of dispensing with an opponent working his way back from a lengthy injury lay-off to win 6-1 6-2 in a little more than an hour in Washington.
He will now face either America's Taylor Fritz or Australian Alexei Popyrin in the next round while Edmund reflects on his return to singles action after 20 months out following three knee operations.
Speaking on court afterwards, Evans said: “My focus was very good. I had a bit of a blip at the end, but I thought I didn't do much wrong. He hit, I think, three winners.
”I'm just really happy to be going still. It's always nice to start a new swing off with a win and it's nice to be through to the third round.”
Top seed Andrey Rublev eased through courtesy of a 6-4 6-2 win over Briton Jack Draper.
The 24-year-old had to remain patient in a tight first set as six break points came and went before he converted the seventh to take a 5-4 lead, and he duly obliged on serve to cement his advantage.
A forehand error from the 20-year-old handed Rublev a second-set break and a 2-1 lead and although he had to save two break points in the next game, he managed to see out a comfortable victory.
Additional reporting by PA.